1. Field of Invention
The present invention relates generally to the field of ad hoc protocols for routing packets between computing devices in a mobile ad-hoc network (MANET) using Time Division Multiple Access (TDMA), and in particular MANETs used for military applications such as the Joint Tactical Radio System (JTRS).
2. Description of Related Art
A mobile ad-hoc network (MANET) is a self-configuring network of mobile router nodes, e.g. wireless laptop personal computers but including airborne, fixed, maritime, vehicular, dismounted and handheld applications, forming a topology. The router nodes may organize themselves in a peer-to-peer, computer-to-computer manner without the use of a central base station (access point).
A mobile ad-hoc network node does not need a priori knowledge of the topology of the network around it. A new node introduced into an MANET can discover the topology by announcing its presence and listening for corresponding announcements from its neighbor nodes. A new node can learn about new near nodes and how to reach them; the new node can announce that it can also reach those nodes. As time progresses each node may know about all other nodes and ways how to reach them. Nodes may grow into the MANET and die from it.
In practice, routing from one node to another in a MANET typically requires an “on-demand routing protocol” such as DSR (Dynamic Source Routing), or AODV (Ad Hoc On Demand Distance Vector). Typical routing protocols necessitate that they: keep routing table reasonably small; choose the best route for a given destination (e.g., based on a quality of service factor such as being the fastest route, most reliable route, highest throughput route, cheapest route or the like); keep routing tables up-to-date when nodes die, move or are added to the MANET; and require a small number of messages or time to converge new nodes into the network and initialize the network.
Numerous ad-hoc network routing protocols have been proposed in the literature, and have been classified into various categories, such as: pro-active (Table-driven); reactive (on-demand); hierarchical; geographical; power aware; multicast; or geographical multicast (geocast).
MANETS may be used in systems such as TDRS (Tactical Data Radio System) and JTRS (Joint Tactical Radio System), such as used for software defined radio (SDR). Historically some of the earliest MANETS were called “packet radio” networks, sponsored by DARPA in the 1970s.
SDR (Software Defined Radio) creates radios that function like computers, where the functionality of a radio is defined by software that can be upgraded, rather than by fixed hardware. SDR has been defined as a radio whose signal processing functionality is defined in software; where the waveforms are generated as sampled digital signals, converted from digital to analog via a high speed Digital-to-Analog Converter (DAC) and then translated to Radio Frequency (RF) for wireless propagation to a receiver. The receiver typically employs an RF subsystem coupled to a high speed Analog to Digital Converter (ADC) that can capture some or all of the channels of the software radio node. The receiver then extracts and demodulates the channel waveform using software executing on a digital processor.
SDR is aimed at solving several of the challenges of over-the-air communications, including compatibility with pre-existing legacy radio systems, ability to emulate transmission and reception of a plurality of different waveforms or forms of modulation (modem control), and more efficient spectrum usage, including operation in different frequency bands, with the lowest possibility of interception, detection and interference from unauthorized parties. The US military through the Department of Defense (DoD) has driven the development of next generation SDR with an Open Standard Architecture standard for implementing Joint Tactical Radio Systems (JTRS), which is used to communicate in military communication systems, through the use of an open standard Software Communications Architecture (SCA). The SCA calls out the following features: a Common Open Architecture; the ability to support multiple domains, including airborne, fixed, maritime, vehicular, dismounted and handheld applications; the ability to operate in multiple frequency bands; compatibility with legacy radio systems; the easy ability to upgrade new technologies to improve performance; enhanced security, including cryptographic capability, user identification and authentication, encryption key management, and multiple independent levels of security classification; networking ability, including support for legacy network protocols; software reusability; and support for plug-and-play and real-time reconfigurability, with waveforms being portable from one implementation to another.